Revealing the Hidden Spin-Polarized Bands in a Superconducting Tl Bilayer Crystal.

ABSTRACT

The interplay of spin-orbit coupling and crystal symmetry can generate spin-polarized bands in materials only a few atomic layers thick, potentially leading to unprecedented physical properties. In the case of bilayer materials with global inversion symmetry, locally broken inversion symmetry can generate degenerate spin-polarized bands, in which the spins in each layer are oppositely polarized. Here, we demonstrate that the hidden spins in a Tl bilayer crystal are revealed by growing it on Ag(111) of sizable lattice mismatch, together with the appearance of a remarkable phenomenon unique to centrosymmetric hidden-spin bilayer crystals a novel band splitting in both spin and space. The key to success in observing this novel splitting is that the interaction at the interface has just the right strength it does not destroy the original wave functions of the Tl bilayer but is strong enough to induce an energy separation.